1. Field of the Invention
This application is related to integrated circuits and more particularly to communications interfaces of integrated circuits.
2. Description of the Related Art
In general, a receiver interface of a communications system uses AC coupling techniques to reduce effects of low-frequency disturbances, e.g., undesirable DC offsets. In addition, AC coupling reduces the need for a common ground reference between integrated circuits on separate printed circuit boards. A conventional receiver interface for AC-coupled communications includes an equalizer to equalize channel loss by attenuating low-frequency energy while maintaining high-frequency energy. High linearity of the equalizer is desired due to a wide-swing of the signals received by the receiver interface. Thus, a conventional receiver interface attenuates low frequencies using a voltage divider circuit, more specifically, a resistor-based network.
The resistor-based network is a DC-coupled circuit that requires an additional AC coupler in many applications (e.g., PCI Express or other AC coupled interface). In addition, the resistor-based network introduces a large parasitic capacitance into the signal path that narrows the overall bandwidth of the receiver. Another drawback of the resistor-based network is the requirement of tuning multiple resistors simultaneously in order to configure low-frequency attenuation or location of a pole of the signal response.